Nutrient addition and light supplementation modulate the growth of Glechoma longituba and soil microbial communities

BACKGROUND: The interactive effects of nutrient supply and light supplementation on medicinal plants remain unclear. This study aimed to investigate these effects on Glechoma longituba, a widely used traditional medicinal plant. METHODS: This greenhouse experiment used a fully factorial design (with/without nutrients, with/without supplemental lighting) to investigate these effects on G. longituba. RESULTS: Nutrient addition and supplemental lighting synergistically increased total mass and node number. Supplemental lighting enhanced the bioactive and nutritional constituents. Nutrient addition increased the levels of protein and sugars but reduced the levels of flavonoids and chlorogenic acid. However, supplemental light partially reversed the decreases in chlorogenic acid. Nutrients were the primary driver of microbial shifts, reducing bacterial diversity but increasing fungal diversity and altering metabolic pathways. Supplemental lighting affected bacterial communities only when no nutrients were added. Bacterial communities correlated with aboveground biomass and root-shoot ratio, indicating roles in nutrient cycling and plant growth promotion. Fungi correlated only with root-shoot ratio, suggesting functions in carbon allocation and resource partitioning. CONCLUSION: Nutrient addition and supplemental lighting synergistically enhance growth but have contrasting effects on medicinal quality of G. longituba. Supplemental lighting improves yield and medicinal constituents, mitigating medicinal quality decline from nutrient addition. Nutrients dominate soil microbial community shifts, while light affects bacteria only under nutrient limitation. These findings reveal the differential regulatory effects of light and nutrients on the yield and medicinal quality of G. longituba, and highlight the importance of balanced nutrient and light management for the sustainable cultivation of this medicinal plant.